Manufacture of leather



Patented Jan; 2, 1934 v 1,94 1,4s MANUFACTURE or LEATHER RichardPasternack, Brooklyn, and Gordon 0. Cragwall, Queens Village, N.- Y.,assignors to Charles Pfizer & Company, Brooklyn, N. Y., a

. 12 Clai s.

This invention relates to the tanning of hides, kips, skins and otherorganic substances containing collagen and has for its object to producewhite or bright colored leathers which are flex- 5 ible, durable andresistant to the action of water as well as other causes of decay.

It is well known that aluminum compounds may be used in tanning leather,but the product has always been considered inferior to that produced byother tanning methods because of the supposed low affinity of collagenfor aluminum, and instability of the combination produced by knownmethods of alum tanning. This situation is recognized in Vol. II of TheChemistry of Leather Manufacture, by J. A. Wilson, page 698 if, whereattention is called to the fact that processing with aluminum compoundsis commonly referred to as tawing to distinguish it i from true orpermanent tanning.

We have found, however, that the defects of previous alum tanningprocesses were due to the use of unsuitable aluminum preparations. Wehave discovered that by treating hides, etc., with a composition ofaluminum and gluconic acid containing 10-24% A1203, and here referred toas aluminum gluconate; either with or without pretreatment withformaldehyde, a leather is obtained which is light colored, flexible anddurable, and resistant to the action of water at a temperature as highas 88 C. In permanence ofcharacteristics it is comparable to the best ofchrome tanned leathers, while its white color is highly advantageous formany purposes.

Many of the aldehydes have been used previously for tanning purposes.They can be used alone to produce a white leather, but such processesrequireafter-treatment with soap or a mild alkali, and the leatherproducedis not of satisfactory durability. i

It is also recognized that the use of formaldehyde as a pre-treatment invegetable tanning processes facilitates the absorption of the tanningagents, and a leather of satisfactory. durability may be prepared bysuch a combination process, but it is necessarily of a brownish colordue to the action of the second tanning agent.

By the use of formaldehyde or other aliphatic aldehyde suitable fortanning purposes, followed by treatment with aluminum gluconate, weovercome the above and other defects of previous processes and obtain awhite product which is also especially suited to dyeing in light orpastel colors. I

In the application of our process we do not limit ourselves to the useof any particular apparatus, but can use any equipment suitable fortanning according to previously known processes. Our process is alsoapplicable to leathers which are to undergo subsequent treatment by 0other tanning processes.

corporation of New Jersey No Drawing. Application July 29, 1931 SerialNo. 553,884

The following examples aregiven as specific illustrations of ourprocess:

Example I Add 100 pounds of skins, previously unhaired, bated, andpickled, to a bath composed of:

. Pounds Water 250 Salt 12 Sodium bicarbonate 3 Formaldehyde, 36% soln10 Th'is'bath is preferably maintained at a temperature of 40-45 C. andis agitated by suitable means for four hours. At the end of this timethe skins are removed and washed with cold Aluminum gluconate,containing 18-19% This bath is agitated by suitable means for four hoursat an initial temperature of 40-45" 0., after which the tanned skins areremoved and washed thoroughly with water at 30-40 C. The.

redrying, being very similar to chrome-tanned leather in this respect.

; In place of formaldehyde, chemically equivalent quantities of otheraliphatic aldehydes may be used. If the color of the finished product isnot important, other tanning agents such as tannin, syn-tan, etc., maybe employed.

Example II Add 100 pounds of skins, previously unhaired, bated andpickled, to a bath composed of Pounds Water 250 Aluminum gluconate,containing 18-19% 'Salt 2 12 This bath is agitated by suitable means fortwentyfour hours, after which the process is completed as in Example I.

Example III- A tanning bath is prepared from 225 lb. gluconicfermentation liquor, containing about 45.2 lb. gluconic acid. To this isadded 4.5 lb. aluminum, previously cut up into smallpieces, washed with10% caustic, rinsed with cold water, and superficially amalgamated bytreatment with a suitable mercury salt, as mercuric gluconate. Uponheating to -60 C., the aluminum dissolves, leaving a finely dividedprecipitate of mercury which is removed by filtration.

To this are added 100 lb. hides, previously unhaired, bated and pickled,and pretreated with formaldehyde as in Example I. The process iscompleted as in Example I.

In each example, in place of aluminum gluconate, the molecularequivalents of an aluminum salt, such as the sulphate, chloride, etc.,and gluconic acid may be used. These solutions should be neutralized toa pH of 4-6 with soda. Instead of aluminum salt, a soluble aluminate maybe used with gluconic acid, adjusted to a pH of 4-6 as before.

The invention claimed is:

1. The step in theprocess of tanning hides and the like which consistsin subjecting same to the action of a bath containing in solutionaluminum and gluconic acid.

2. The step in the process of tanning hides and the like which consistsin subjecting same to the action of a bath containing aluminumgluconate.

3. The step in the process of taming hides and the like which consistsin subjecting same to the action of a bath containing an aluminum saltand gluconic acid. v

4. The step in the process of tanning hides and the like which consistsin subjecting same to the action of a bath containing a water-solublecomposition of aluminum and gluconic acid whose A1203 content is between10% and 24%.

5. The step in the process of tanning hides and the like which consistsin subjecting same to the action of a bath containing a solublealuminate and gluconic acid, and adjusted to pH 46.

.6. The process of tanning hides and the like which comprises subjectingthe hides to the action of an aliphatic aldehyde and then subjectingthem to the action of a bath containing in solution aluminum andgluconic acid.

7. The process of tanning hides and the like which comprises subjectingthe hides to the action of formaldehyde and then subjecting them to theaction of a bath containing in solution aluminum and gluconic acid.

8. The process of tanning hides and thelike which comprises subjectingthe hides to the action of formaldehyde and then subjecting them to theaction of a bath containing aluminum gluconate.

'9. As a new product, leather tanned by the action of a water-solublecomposition of aluminum and gluconic acid.

10. As a new product of manufacture, white flexible and durable leathertanned and made resistant to the action of water up to 88 C. by theaction of aluminum gluconate.

11. As a new product of manufacture, a composition containing theresidues of the action of formaldehyde, followed by a water-solublecomposition of aluminum and gluconic acid upon hide proteins.

12. The step in the process of tanning hides and the like which consistsin subjecting same to the action of a bath containing in solution analuminum compound and gluconic acid, neutralized to pH 4-6.

RICHARD PASTERNACK. GORDON O. CRAGWALL.

